This invention relates to a cyclone separator and, more particularly, to a cyclone separator in which the heat exchange portion of the hopper section of such separator is extended.
Fluidized bed reactors, combusters, or gasifiers are well known. In these arrangements, air is passed through a bed of particulate materials, including a fossil fuel such as coal and an adsorbent for the sulfur generated as a result of combustion of the coal, to fluidize the bed and to promote the combustion of the fuel at a relatively low temperature. When the heat produced by the fluidized bed is utilized to convert water to steam, such as in a steam generator, the fluidized bed system offers an attractive combination of high heat release, high sulfur adsorption, low nitrogen oxide emissions, and fuel flexibility.
The most typical fluidized bed combustion system is commonly referred to as a bubbling fluidized bed in which a bed of particulate materials is supported by an air distribution plate, to which combustion-supporting air is introduced through a plurality of perforations in the plate, causing the material to expand and to take on a suspended, or fluidized state. In the event the reactor is in the form of a steam generator, the walls of the reactor are formed by a plurality of water-cooled heat transfer tubes. The heat produced by a combustion within the fluidized bed is transferred to a heat exchange medium, such as water, steam, or a combination thereof, circulating through the tubes. The tubes are usually connected to a natural water circulation circuitry, including a steam drum, for separating water from the steam thus formed which is routed to a turbine to generate electricity or to a steam user. The tubes eliminate the need for expensive, high temperature refractory-lined duct work and expansion joints.
Fluidized bed combustion systems of this type include a cyclone separator which is normally situated to receive the gaseous discharge from the bubbling fluidized bed. The material introduced into the separator contains gases with solid fuel particles entrained. The separator utilizes centrifugal forces to separate the solid particles from the gases.
Cyclone separators for separating solid fuel particles and gases discharged from a combustion system or the like are normally provided with a hopper section in the lower end to collect the solid fuel particles. U.S. Pat. No. 4,944,250 discloses an improved cyclone separator having walls constructed of water-cooled heat transfer tubes. The addition of the tubes minimizes the need for expensive, high temperature refractory-lined duct work and expansion joints between the reactor and the cyclone separator, and between the cyclone separator and heat recovery section. The walls of the separator are constructed of constant diameter tubes connected together by fins. Each fin extends from one tube and is welded to an adjacent tube, thus creating a gas-tight wall. In this design the hopper section of the separator is conically-shaped, with the circumference and diameter of the hopper section decreasing from top to bottom. Thus, while the circumference of the hopper section decreases, the diameters of the tubes in the walls remain constant. To accommodate the decreasing circumference, the size of the fins connecting the tubes in the walls is gradually decreased from top to bottom. The problem arises when the size of the fins connecting the tubes is no longer able to be reduced because the tubes are touching one another with no room for a fin. As this problem occurs at some area above the bottom of the hopper section, the tubes cannot extend the full length of the hopper section.
One solution to this problem is to introduce an intermediate ring header, which reduces the number of tubes extending between the intermediate ring header and the lower ring header and thus enables the tubes to extend the full length of the hopper section. However, the addition of the intermediate ring header increases the cost of the system.